In data storage system read channel operations, read and servo events are typically prepended with periodic signals, often referred to as “preamble” signals, with substantially uniform transition spacing to align phase and gain prior to data recovery. Gain or phase errors are sometimes encountered as result of defects in storage media or environmental forces. During the signal acquisition process, gain and phase errors can significantly complicate the recovery process. It is thus advantageous to determine signal quality prior to data recovery.